This invention relates generally to large lifting equipment, such as cranes and the like, and more specifically to grippers, or grapples, which are on lifting machines, such as at the ends of crane cables, for attaching the lifting machines to items to be lifted.
As is well known, lifting machines, such as cranes and the like, are widely used at construction sites, as well as at other loading and unloading sites, for lifting heavy items, such as construction I-beams. A general problem that has often been encountered when such lifting machines have been detached from lifted items is that it has been necessary for workmen to position themselves at dangerous locations to do this. In this regard, for example, chokers have been commonly used at construction sites for attaching crane cables to construction beams, such as I-beams. These chokers have normally been in the form of sliding loops which tighten onto the I-beams. In order to properly loosen these chokers, it has been necessary for workmen to be physically located where the chokers are attached to the beams and to do it by hand. Quite often I-beams are placed in extremely dangerous locations where it is difficult and dangerous for workmen to release the chokers.
Thus, it is an object of this invention to provide a power gripper for lifting machines which can be disengaged from items to be lifted without a worker being positioned at a point of engagement. More specifically, it is an object of this invention to provide a power gripper which can be engaged and disengaged without requiring iron workers to go out onto beams, or climb vertical beams.
A number of prior-art devices have been suggested for accomplishing the above-stated objects. For example, U.S. Pat. No. 5,580,113 to Pomerville et al. describes a remote control crane/load safety shackle which includes a linear actuator for driving an actuator rod for supporting a load. A radio remote control unit can be used to selectively extend and retract a pin of the shackle. A major disadvantage of such a system is that construction sites have a great deal of machinery located thereat, including telephones, radios, and other equipment creating sparks, radio static and other interferes which cause malfunctions in radio remote control devices. If a power gripper is inadvertently caused to prematurely release, a falling load can cause a great deal of damage. U.S. Pat. No. 4,293,155 to Grant, and U.S. Pat. No. 3,647,255 to Hale et al., have similar teachings of radio-controlled power grippers. Therefore, it is another object of this invention to provide a lifting machine power gripper whose operation is extremely reliable and responsive only to signals fed thereto by authorized operators thereof.
Further, it is an object of this invention to provide components for machinery, such as lifting grippers.
It is also an object of this invention to provide a lifting power gripper which is easy and reliable to use, but yet which is reasonably inexpensive to construct.